JPS6147065B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to step motors, and more particularly to step motors in which the polarity of excitation is controlled and circumferentially arranged by energizing at least two different coils to cause the rotor to step. The present invention relates to a step motor containing circumferentially arranged permanent magnets that cooperate with magnetic pole teeth. The main object of the present invention is to provide a step motor which has a relatively large output in relation to its outer diameter or volume. Another object of the present invention is to provide a step motor that can be mass-produced at low cost without using complicated tools. Another object of the present invention is to provide a step motor that reliably stops when turned off so that the output shaft can be maintained at the same position that the shaft occupied immediately before being turned off, even after the step motor is turned off. Still another object of the present invention is to provide a step motor that is relatively simple in construction and has a long life. Other objects and advantages of the invention will become apparent from the following description. The present invention comprises a common axis, a rotor and a stator aligned with the common axis, and further includes first magnetic poles that mesh with each other in a first plane orthogonal to the common axis in which the rotor or the stator is disposed. teeth and second magnetic pole teeth that mesh with each other in a second plane parallel to the first plane; and
first and second coils that excite the outer and inner magnetic pole teeth of the magnetic pole teeth to different polarities, respectively;
The first and second magnetic pole teeth are arranged in a rotor or a stator in which no magnetic pole teeth are arranged, and two adjacent magnetic pole teeth are spaced apart from each other in the circumferential direction so as to be located between the first and second magnetic pole teeth, and the first and second magnetic pole teeth are arranged with different polarities. The present invention provides a step motor comprising a plurality of permanent magnets aligned between first and second magnetic pole teeth excited by two coils. Hereinafter, the present invention will be explained along with preferred embodiments. The step motor shown in FIGS. 1 and 2 includes a disc-shaped rotor 10, a first stator portion, that is, a left portion 11a, and a second stator portion, that is, a right portion 11b, which face the front surface of the rotor 10, respectively. A stator is included. The rotor 10 and the left part 11a and right part 11b of the stator are the shaft 1
2, the rotor 10 is mounted around a non-magnetic hub 13 attached to the end of the shaft 12. Shaft 12 extends from hub 13 through a non-magnetic bearing sleeve 14 in left portion 11a. a snap spring 15 inserted into a groove at the outer end of the spline of the shaft 12;
The shaft 12 is held in a predetermined axial position by a non-magnetic hub 13 located near the inner end of the non-magnetic bearing sleeve 14. The inner peripheral surfaces of the left portion 11a and the right portion 11b are formed of cylinders 16 and 17 made of a magnetically permeable material such as soft iron. Left part 11
The outer circumferential surfaces and outer end surfaces of the right portion a and the right portion 11b are respectively formed of cylinders 18 and 1 with one end surface closed. That is, the outer circumferential surfaces of the left part 11a and the right part 11b are formed by cylinders 20 and 21 of cylindrical bodies 18 and 19, respectively, which are arranged at a predetermined distance from the outer circumferential surface, and the outer end surfaces are formed by the cylinders 20 and 21 of the cylindrical bodies 18 and 19, respectively. ，
Annular wall surfaces 22 and 23 that close one end surface of 21
It is divided by. Two sets of cylinders 16,2
0 and 17, 21, as detailed below,
A set of coils 24, 25 is provided for suitably energizing multiple sets of intermeshed stator poles extending perpendicular to the motor axis. The left part 11a and the right part 11b of the stator are formed of a non-magnetic material such as aluminum, and are opposed to each other with an annular spacer 26 interposed therebetween for suitably positioning the outer magnetic pole teeth of the left part 11a and the right part 11b. ing. An annular member 31 having magnetic poles 31a and 32a extending perpendicularly to the motor axis on the same plane and meshing with each other is provided on the opposing end surfaces of the cylinders 18 and 19, respectively.
32, and annular members 33 and 34 extending perpendicularly to the motor axis on the same plane and having magnetic poles 33a and 34a that are engaged with each other are arranged.
The annular members 31-34 are made of a magnetically permeable material such as soft iron. The outer annular members 31, 33 each include six outer magnetic pole teeth 31a, 33a,
and are fitted into inner grooves bored in the closed ends of the cylinders 18, 19, forming a low magnetic resistance circuit for the magnetic flux induced in the cylinders 20, 21 by the respective coils 24, 25. are doing. On the other hand, annular member 3
2 and 34 are six inner magnetic pole teeth 32a and 34a, respectively.
and is formed integrally with the cylinders 16 and 17, forming a low magnetic resistance circuit for the magnetic flux induced in the cylinders 16 and 17 by the respective coils 24 and 25. Inner/outer magnetic pole teeth 31 of left part 11a of stator
Inner/outer magnetic pole teeth 3 between a and 32a or right part 11b
In order to minimize the leakage of magnetic flux between 3a and 34a, the opposing surfaces of the magnetic pole teeth of the annular members 31 and 32 and the opposing surfaces of the magnetic pole teeth of the annular members 33 and 34 are preferably spaced apart from each other in the radial and circumferential directions. has been done. More specifically, the magnetic pole teeth 31a, 32a are opposed to each other via a radially extending gap 35 and a circumferentially extending gap 36, and the magnetic pole teeth 33a, 34a are opposed to each other via a radially extending gap 37 and a circumferentially extending gap 36. (See FIGS. 3 and 4).
The gaps 35 to 38 are sufficiently large so that the magnetic flux between the magnetic pole teeth 31a to 34a and the cylinders 16 and 1 is larger than the magnetic flux flowing between the adjacent magnetic pole teeth 31a and 32a or between the mutually adjacent magnetic pole teeth 33a and 34a.
The amount of magnetic flux flowing between the permanent magnets 7, 20, 21 or the rotor 10 is overwhelmingly larger. In the illustrated embodiment, each of the left and right parts of the stator includes 12 magnetic pole teeth arranged at equal intervals in the circumferential direction and meshed with each other, but if the number of magnetic pole teeth is different, It will be clear that the step angle can be varied. Next, the rotor 10 will be explained. Permanent magnetization (hereinafter referred to as PM) regions 40 are arranged at equal intervals near the circumference of one ceramic ring 41 fixed to the hub 13. PM area 40
The center of the stator is spaced apart from the motor shaft by approximately the same distance as the distance from the motor shaft of the stator's magnetic pole teeth 31a to 34a, which are arranged opposite to the rotor 10.
Therefore, a pair of magnetic gaps 42, 43 are formed between both end faces of PM region 40 and magnetic pole teeth 31a to 34a. All of the PM regions 40 are magnetized in the direction of the motor shaft, and adjacent regions are magnetized in opposite directions as indicated by N and S in FIG. If desired, permanent magnets may be mounted on non-magnetic bearings fixed to the hub 13 to form the rotor. Cylinder 20 of left part 11a and right part 11b,
Since an annular spacer 26 that magnetically shields the rotor 10 surrounds the rotor 10, magnetic flux passing between the left portion 11a and the right portion 11b must pass through the PM region of the rotor. The annular spacer 26
Six alignment members 51 and 52 are formed on both side surfaces of the stator and extend into the gap between the inner and outer magnetic pole teeth 31a, 32a and 33a, 34a of the stator, respectively, and are spaced apart from each other in the circumferential direction. There is.
The alignment members 51 and 52 each have two sets of inner and outer annular members 31, 32 and 3 at desired positions in the circumferential direction.
3,34 are held accurately. Aligning member 51,
52 is suitably fitted between mutually adjacent outer magnetic pole teeth 31a and between mutually adjacent outer magnetic pole teeth 34a to hold the annular members 31, 33 in place. In order to hold the inner magnetic pole teeth 32 and 34, the inner magnetic pole teeth 32 and 34 are provided on the inner surfaces of the alignment members 51 and 52.
A central recess 51a or 52a is provided (52a not shown) for receiving and retaining the tip of a, 34a. Since the outer magnetic pole teeth 31a and the inner magnetic pole teeth 32a are in contact with different end surfaces of the coil 24,
Outer magnetic pole teeth 31a and inner magnetic pole teeth 3 adjacent to each other
2a is magnetized in the opposite direction. Similarly, the outer magnetic pole teeth 33a and the inner magnetic pole teeth 34a are connected to the coil 25, respectively.
Since the outer magnetic pole teeth 33a and the inner magnetic pole teeth 34a that are adjacent to each other are in contact with different end surfaces of the magnetic pole teeth 33a and 34a, they are magnetized in opposite directions. Since the coils 24 and 25 are wound around the motor shaft, the coil 24
The directions of the magnetic fluxes induced in the cylinders 16, 20 adjacent to the coil 25 are opposite to each other, and the directions of the magnetic fluxes induced in the cylinders 17, 21 adjacent to the coil 25 are also opposite to each other. The direction of the magnetic flux induced in the inner cylinders 16, 17 is therefore always opposite to the direction of the magnetic flux induced in the outer cylinders 20, 21, respectively. Furthermore, the polarity of the outer magnetic pole tooth 31a and the inner magnetic pole tooth 32a is opposite, and the polarity of the outer magnetic pole tooth 33a and the inner magnetic pole tooth 34a is opposite, and the polarity is the same as that of the coils 24 and 25. Determined by the direction of the current. A switching circuit is provided which reverses the direction of the current each time one of the coils 24, 25 is energized to control the direction of stepping of the rotor 10, as will be explained in more detail below. When the coil 24 on the left side 11a of the stator or the coil 25 on the right side 11b of the stator is energized, the rotor 1
0 PM region 40 is the nearest opposite polarity magnetic pole tooth 3
It is attracted to 1a to 34a. For example, as shown in FIG. 3, the left part 11a of the stator has magnetic pole teeth 31a, 3
2a, the magnetic flux induced in the outer cylinder 20 is excited to the N pole outer magnetic pole tooth 31a.
, and further enters the PM region 40 in the rotor 10 whose end face facing the magnetic pole teeth 31a is the S pole. At the same time, magnetic flux flows from the north end face of the PM region 40 in the rotor 10 to the magnetic flux induced in the inner cylinder 16 via the inner magnetic pole teeth 32a excited to the opposing south pole. Magnetic flux flows from the cylinder 16 to the annular wall surface 22 of the cylindrical body 18 . Third
The magnetic flux shown in the upper half of the figure maintains the rotor 10 in the position shown unless the excitation current of at least one of the coils 24, 25 changes. Since the left part 11a and the right part 11b of the stator each include 12 magnetic pole teeth, namely 6 outer magnetic pole teeth and 6 inner magnetic pole teeth, the left part 11a
The pitch of the magnetic pole teeth of the right portion 11b is 30 degrees. Further, the magnetic pole teeth 33a, 34a of the right portion 11b are offset by 15 degrees with respect to the magnetic pole teeth 31a, 32a of the left portion 11a. The pitch of the PM region 40 of the rotor 10 is the left part 11a or the right part 11 of the stator.
It is the same as the pitch of the magnetic pole teeth in b, that is, 30 degrees.
Therefore, as shown in FIG. 3 and FIG.
a, 32a, the magnetic pole teeth 33a, 34a of the right portion 11b are aligned with the non-magnetized region between the PM regions 40. Further, as shown in FIGS. 4 and 4a, the PM region 40 of the rotor 10 is located in the right portion 11b.
When aligned with the magnetic pole teeth 33a, 34a of the left part 1
The magnetic pole teeth 31a, 32a of 1a are aligned with the non-magnetized region between the PM regions. Since the magnetic pole teeth on the left side 11a and the magnetic pole teeth on the right side 11b of the stator are offset from each other, the magnetic pole teeth on the left side 11a or the right side as shown using magnetic flux lines in FIGS. The magnetic pole teeth of the portion 11b effectively act as a return path for the magnetic flux passing through the magnetic pole teeth of the right portion 11b or the left portion 11a and the PM region 40 of the rotor 10. That is, the return path of the magnetic flux loop shown at the top of FIG.
The magnetic resistance of the return path is formed by the inner magnetic pole teeth 34a of the inner cylinder 17 and the cylindrical body 19.
This is significantly smaller than the magnetic resistance of the base steel. Similarly, in the case of the magnetic flux loop shown in the lower part of FIG. This is significantly smaller than the magnetic resistance of . The four magnetic flux loops shown in Figures 3 and 4 are:
Four different driving states are shown, each of which sequentially steps the rotor 10 through an angle of 15 degrees. More specifically, the upper magnetic flux loop in FIG. 3 indicates that the coil 24 is energized by the current If flowing in the first or forward direction, and the lower magnetic flux loop in FIG. Due to the current If flowing in the direction of , that is, the forward direction, the coil 25
indicates that it is energized. The upper magnetic flux loop of FIG. 4 indicates that the coil 24 is energized by a current I _f flowing in a second or reverse direction, and the lower magnetic flux loop of FIG. This shows that the coil 25 is energized by the current I _f flowing through. To explain the four driving states in more detail, the four driving states are as follows.
Stator magnetic pole teeth 31 corresponding to two driving states
a, 32a, 33a, 34a and PM area 40
The positional relationships between the two are shown in partial cross-sectional views in FIGS. 5 to 8. The driving states corresponding to the lower magnetic flux loop in FIG. 3 and the upper magnetic flux loop in FIG. 4 are as follows:
Not shown in FIGS. 5 to 8, the rotor 10
It will be clear that this corresponds to the case where is displaced by an additional 15 degrees. 3-8, the rotor 10 is successively stepped in 15 degree increments, or half a pole tooth pitch, by deenergizing the energized coils and energizing the other coils. Each time the coil is energized, the direction of the energizing current is reversed. Therefore, when the rotor 10 is in the position of FIGS. 3, 3a, and 5 and it is desired to step the rotor clockwise, the coil 24 is deenergized so that the outer pole tooth 33a is at the south pole and the inner pole tooth 33a is at the south pole. The coil 25 is energized so that 34a becomes the N pole, that is, to create the magnetic flux loop shown in the lower part of FIG.
4a and 6). As a result, the rotor 10 is moved clockwise in steps of 15 degrees so that it faces the right side 11b of the stator and has a polarity of N.
The magnetic pole faces 33a and 34 of the PM region 40, which are the pole and the south pole, are excited to the south pole and the north pole, respectively.
Make it consistent with a. Similarly, when it is desired to step the rotor 10 counterclockwise, the coil 24 is deenergized and the coil 25 is energized so that the outer magnetic pole tooth 33a becomes the north pole and the inner magnetic pole tooth 34a becomes the south pole. This moves the rotor 10 counterclockwise by 15 degrees so that it faces the right side 11b of the stator and has a polarity of S.
The magnetic pole faces 33a and 34 of the PM region 40, which are poles and north poles, are excited to the north pole and south pole, respectively.
Make it consistent with a. Producing the third drive condition shown by the upper magnetic flux loops of FIGS. 7 and 4 causes rotor 10 to move an additional 15 degrees clockwise. This is accomplished by deenergizing the coil 25 and energizing the coil 24 so that the outer magnetic pole tooth 31a becomes the south pole and the inner magnetic pole tooth 32a becomes the north pole, as shown in FIG. As a result, the rotor 10 is moved in steps of 15 degrees clockwise, and the PM region 4 facing the left part 11a of the stator and having the north and south polarities is moved.
The magnetic pole faces of 0 are aligned with the magnetic pole teeth 31a and 32a which are excited to the S and N poles, respectively. As described above, the magnetic pole teeth 31a, 32a and 33
The positional relationship between the magnetic pole teeth 31a and 34a and the rotor 10 is in the initial state shown in FIG.
The polarity of a is reversed. Rotor 16 remains in this position until the energization of coils 24 and 25 changes. To further move the rotor 10 in a clockwise direction, the magnetic pole teeth 33a, 34 as shown in FIG.
a can be excited to form the magnetic flux loop shown in the lower part of FIG. At this time, the coil 24 is deenergized and a current flows through the coil 25 in the opposite direction to that shown in FIG. Therefore, the outer magnetic pole tooth 33a is excited to the north pole, and the inner magnetic pole tooth 34a is excited to the south pole. As a result, the rotor 10 is further moved by 15 degrees in a clockwise direction, and the magnetic pole faces of the PM region 40, which faces the right side 11b of the stator and whose polarities are S and N poles, are excited to N and S poles, respectively. magnetic pole teeth 33
a, 34a. Therefore, the magnetic pole teeth 31
The positional relationship between a, 32a, 33a, and 34a and the rotor 10 is as shown in FIG. 4a, but the polarity of the magnetic pole teeth is induced by the magnetic flux loop shown at the bottom of FIG. 4 in the second driving state. The opposite is the case. This completes the four driving states of the step motor of the present invention, and then, as described above, the first driving state shown by the magnetic flux loop at the top of FIGS. 5 and 3 is resumed and the step operation is performed. Continued. One advantage of the step motor of the present invention is that the coil 2
The reason is that even when both 4 and 25 are de-energized, they are reliably stopped. Therefore, the minimum reluctance or stop position of the rotor when one of the coils 24, 25 is energized is the stop position when both coils 24, 25 are de-energized and the only source of magnetic flux is the PM region 40 of the rotor 10. It's also the location. At four stop positions, that is, drive positions, formed by energizing one of the coils 24 and 25, the PM region 40 moves toward the magnetic pole tooth 3.
It will be clear from FIGS. 5-8 that it is fully aligned with one of 1a, 32a or 33a, 34a. The four stopping positions are the coil 2
Regardless of whether 4, 25 is energized or not,
This is also the position where the magnetic resistance to the magnetic flux flowing between the north and south poles of the PM region 40 is the minimum. Therefore, when the motor 10 is turned off, i.e. the coils 24,
When both coils 25 are deenergized, the holding force is weaker than when at least one of both coils 24 and 25 is energized, but the rotor 10 is not displaced and is securely held by the PM region 40. There is. Another advantage of the step motor of the present invention is that one set of intermeshed pole teeth is offset circumferentially by a half pitch from another set of intermeshed pole teeth, so that the holding force is reduced. It is to be maximum in both the energized and deenergized states of the motor. This is because one set of pole teeth is always aligned with respect to the non-magnetized region between the PM regions 40 and thus the rotor 10
This is because a magnetic path with low magnetic resistance is provided as a return path for the magnetic flux flowing between the north and south poles of the PM region 40. That is, if the two sets of magnetic pole teeth of the stator are aligned with each other, unlike the step motor of the present invention, the magnetic flux will be distributed between the wall surfaces 22 and 23 on both sides of the rotor 10 and the inner and outer cylinders 16 and 2.
It must always flow through a long high reluctance circuit consisting of 0, 17, 21. This is the case when the motor 10 is in the on and off states. However, since the two sets of magnetic pole teeth of the stator are circumferentially offset from each other, it is clear from the magnetic flux conditions shown in Figures 3 to 8 that the path of the magnetic flux is always confined to one side of the rotor. Will. This maximizes the strength of the magnetic field within the magnetic gaps 42, 43, which in turn maximizes the holding force and output of the motor. Furthermore, this high output is achieved despite the fact that the outer diameter or overall size of the motor is relatively small. A control circuit for controlling energization and deenergization of the coils 24 and 25 by connecting the power supply VI is briefly shown in FIG. Switching element SA of this control circuit
1. SA2, SB1, and SB2 are normally composed of transistors or other semiconductor elements that are turned on and off according to control signals, but in Fig. 9, switching elements that are continuously opened and closed are simply shown. Illustrated. Switching element SA1,
SA2 controls the current flowing through the coil 24, and switching elements SB1 and SB2 control the current flowing through the coil 25. It will be clear that the switching elements SA1, SA2, SB1, SB2 are connected in two ways to the two coils 24, 25, respectively. Close switching element SA1 and close the other three switching elements SA.
2, when SB1 and SB2 are opened, the coil 24 is energized by the downwardly flowing current I _f as shown in FIG. A driving state is created. To deenergize the coil 24 and energize the coil 25 with the downward current I _f , the switching element SA1 is opened, the switching element SB1 is closed, and the other two switching elements SA2, SB2 are activated.
You can leave it open. This creates a second drive condition illustrated in FIG. 6 and corresponding to the lower flux loop of FIG. A current I that deenergizes the coil 25 and flows in the opposite direction
To energize the coil 24 by _r , it is sufficient to open switching element SB1 and close switching element SA2. This creates a third drive state illustrated in FIG. 7 and corresponding to the upper flux loop of FIG. To create the fourth driving state shown in FIG. 8 and corresponding to the lower magnetic flux loop in FIG. 3, switching element SA2 is opened and switching element SB2 is closed. Thereby, the coil 25 can be energized and the coil 24 can be deenergized by the current I _r flowing in the opposite direction. Therefore, four switching elements SA at the same time
By closing only one switching element among 1, SA2, SB1, and SB2, the four driving states shown in FIGS. can. The opening/closing operation of the above-mentioned switching element is shown in the following table. Here, the "X" indicates that the switch is closed.

[Table] To rotate the rotor in the opposite direction, simply reverse the opening and closing operations of the switching elements shown in the table above. The energization of the coil due to the opening and closing operations of the switching elements shown in the above table will be explained using a waveform as a function of time in FIG. Two waveforms A and B indicate the operating states of the coils 24 and 25, respectively, and the "+"
The regions indicate that a current in one direction, such as If, _flows , and the "-" region indicates that a current, for example, _Ir , flows in the opposite direction. Therefore, waveform A shows that the coil 24 is
It shows that it is energized by the current _If over the period from t ₀ to t ₁ . Waveform B, on the other hand, shows that coil 25 is deenergized over the period from t ₀ to t ₁ . Coil 2 at time t ₁
4 is deenergized and coil 25 is energized by the current If over the period from t ₁ to t ₂ . At time _t2 , coil 25 is deenergized and coil 24 is at time _t2
It is again energized by the current I _r over the period from t 3 to t ₃ . At time t ₃ the coil 24 is again deenergized and the coil 25 is reenergized by the current I _r for the period from t ₃ to t ₄ . It will be appreciated that the rotor 10 moves in consecutive steps of 15 degrees at the beginning of each period t ₀ -t ₁ , t ₁ -t ₂ , t ₂ -t ₃ , t ₃ -t ₄ . FIG. 11 shows the opening/closing operation of the switching element in another embodiment of the step motor of the present invention. In this case, the two sets of pole teeth are not offset by half a pitch from each other, but are aligned with each other. At this time, the two sets of magnetic pole teeth are energized at the same time, but the polarity is different, and the stable stopping position of the rotor 10 is the intermediate position in the circumferential direction of the two sets of magnetic pole teeth facing each other, and the two sets of magnetic pole teeth facing each other. Located at the position of the set of magnetic pole teeth. Therefore, the coil 24 in FIG. 11 is energized by the current I _r over a period from t ₀ to t ₂ , and the outer magnetic pole tooth 31a becomes the S pole and the inner magnetic pole tooth 3
2a is excited to the north pole. Coil 25 is from t ₀ to t ₁
energized by the current I _f over a period of
The outer magnetic pole tooth 33a is the N pole and the inner magnetic pole tooth 34a is the N pole.
is excited to the south pole. This causes the rotor to be in a position where the PM region 40 is circumferentially aligned with the stator pole teeth, since each set of pole teeth facing each other across the rotor has an opposite magnetic pole. At time _t1 , the energization state of the coil 24 does not change, but the current in the coil 25 is reversed from If _{to Ir ,} and the outer magnetic pole tooth 33a becomes the S pole and the inner magnetic pole tooth 3
4a is excited to the N pole. This causes the rotor to move in steps of 15 degrees to a new stable position. That is, since the two sets of magnetic pole teeth facing each other across the rotor have the same polarity, the PM region 40 is aligned with the gap between the magnetic pole teeth of the stator. In this case, the two magnetic forces acting on the rotor 10 are balanced when the PM region is aligned with the gap between the pole teeth. At time _t2 , the energization state of the coil 25 does not change, but the current in the coil 24 is reversed from I _r to I _f ,
The outer magnetic pole tooth 31a is the N pole and the inner magnetic pole tooth 32a is the N pole.
is excited to the S pole. Thus, each set of pole teeth facing each other across the rotor once again has an opposite polarity, and the rotor steps 15 degrees to a new stable position. In this case, the PM region 40 is aligned with the stator pole teeth. At time _t3 , the coil 24 is energized by the current _If , but the current in the coil 25 is reversed from _Ir to _If , which in turn reverses the polarity of the magnetic pole teeth 33a, 34a, and the rotor Rotated an additional 15 degrees. When the rotor is in this new stable position, rotor 1
Since the two sets of pole teeth facing each other through 0 are again of the same polarity, the PM region 40 is again aligned with the gap between the stator pole teeth. In this manner, the rotor continues to step until the opening/closing operation of the switching element shown in FIG. 11 is interrupted. Although the step motor described above includes an annular body having a permanent magnet as a rotor and two sets of mutually meshed magnetic pole teeth as part of a stator, it is clear that these configurations may be reversed. Will. Therefore, the annular body 41 having a permanent magnet is pivotally supported on the shaft 12 and fixed to the non-magnetic annular spacer 26 to function as one stator, and the two sets of mutually meshed magnetic pole teeth are fixed to the shaft 12. It may also be made to act as a rotor. It will be clear from the above description that the step motor of the present invention is capable of producing a relatively large output considering its outer diameter or volume. The step motor of the present invention can be mass-produced at low cost, and since the structure of each component is simple, no complicated tools are required. Furthermore, since the step motor of the present invention can be reliably stopped even when turned off, the output shaft can be maintained at the position when the motor was turned off. Furthermore, since the structure is simple, the lifespan is long.

[Brief explanation of the drawing]

1 is a longitudinal cross-sectional view of a step motor according to the present invention, FIG. 2 is a cross-sectional view taken approximately along line 2--2 in FIG. 1, and FIG. 3 is a cross-sectional view of the step motor of FIGS. 1 and 2. FIG. 3A is a partially enlarged sectional view of the motor in FIG. 3, FIG. 4 is a perspective view of the motor in FIG. 3 in different operating states, and FIG.
5 to 8 are simplified partial sectional views of the rotor and stator pole teeth of the motor shown in FIG. 1, and FIG. 9 is a partial enlarged sectional view of the motor shown in FIG. 10 and 11 are explanatory views of the switching circuit for controlling the coil, and the opening/closing operation of the switching element for energizing the coil. 10...Rotor, 11...Stator, 11a...
...Left part, 11b...Right part, 12...Shaft, 1
3...Hub, 14...Bearing, 15...Snat spring, 16,17...Cylinder, 18,1
9... Cylindrical body, 20, 21... Cylinder, 22, 2
3... Wall surface, 24, 25... Coil, 26... Annular spacer, 31 to 34... Annular member, 31
a, 32a, 33a, 34a...magnetic pole teeth, 35,
37...gap, 36, 38...gap, 4
0...PM area, 41...Ring, 42, 43...
... Gap, 51, 52 ... Alignment member, 51a,
52a...Groove, SA1, SA2, SB1, SB2...
switching element.

Claims (1)

[Claims] 1. In a step motor having a rotor and a stator mutually aligned about a common axis, inner pole teeth and outer pole teeth radially and circumferentially spaced apart from the inner pole teeth are contained in one of the rotor and the stator. , each extending perpendicularly to the common axis and spaced apart from each other in the axial direction;
and a set of magnetic pole teeth in which one magnetic pole tooth group is offset in the circumferential direction with respect to the other magnetic pole tooth group; a set of coils for exciting the inner and outer magnetic pole teeth of the tooth group to different polarities; It is located in the axial direction between the magnetic pole tooth groups, and when one of the coils is energized, it is attracted and aligned with the magnetic pole tooth group associated with this coil, and is positioned between another magnetic pole tooth group, and is in an energized state. a plurality of permanent magnets arranged to form a return path for magnetic flux passing through a set of magnetic pole teeth associated with the coil in the coil, and each permanent magnet arranged to be aligned with one of the set of magnetic pole teeth when deenergized; A step motor comprising a device that alternately energizes coils and alternately magnetizes groups of magnetic pole teeth associated with the energized coils to different polarities.